A storage can is able to hold various commodities, for example, foods, tea leaves and coffee beans that need to be kept dry. A conventional storage can provide only an airtight effect, and blocks external air from entering therein so as to prevent the commodities from absorbing moisture in the air and thus from damping the commodities. However, each time when a storage can is opened, the commodities come into contact with new external air and absorb new moisture. As a result, with such repeated opening and closing of a storage can, it is possible that the commodities in the container become damped.
To reduce the moisture absorbed by the commodities in a storage can, a unidirectional air valve is conventionally disposed on a can body or cover of a storage can, and a vacuum device is used to suck out the air in the storage can after the storage can is closed, hence keeping a negative pressure state in the storage can. Thus, the amount of air with which the commodities in the storage come into contact can be reduced and the commodities are then prevented from damping.
To prevent a user from being unable to find an available vacuum device such as a vacuum cleaner or an air extraction rod, for example, the U.S. Pat. No. 5,803,282, “Vacuum Indicator for a Bottle”, discloses a storage can that can be vacuumed. An air pump element is directly designed on a cover of the storage can to allow a user to use the air pump device to pump out the air in the storage can. However, in such conventional design and structure, the air pump element frequently has issues of inappropriate use or damage by external forces. Further, the structure of the outer cover thereof is quite complex, and thus has issues of a high defective rate and high assembly costs.